Efficient nursery plant production of dwarf cogongrass (<i><scp>I</scp>mperata cylindrica</i><scp> L</scp>.) through mass propagation in liquid culture

<jats:title>Abstract</jats:title><jats:p>Dwarf cogongrass (<jats:styled-content style="fixed-case">I</jats:styled-content><jats:italic>mperata cylindrica</jats:italic> <jats:styled-content style="fixed-case"> L</jats:styled-content>.) was developed as a dwarf mutant through heavy‐ion beam irradiation 7 years ago. The dwarf mutant could be expected to use as a new variety for a cover plant with low maintenance, although it has poor seed fertility. To establish an efficient nursery production system for dwarf cogongrass, we attempted mass propagation of it in liquid culture and investigated the genetic stability of its regenerants. Multiple‐shoot clumps (<jats:styled-content style="fixed-case">MSC</jats:styled-content>s) were initiated from apical meristems of dwarf cogongrass on <jats:styled-content style="fixed-case">M</jats:styled-content>urashige and <jats:styled-content style="fixed-case">S</jats:styled-content>koog (<jats:styled-content style="fixed-case">MS</jats:styled-content>) solid medium supplemented with 0.1 mg L<jats:sup>−1</jats:sup> 2,4‐dichlorophenoxyacetic acid (2,4‐<jats:styled-content style="fixed-case">D</jats:styled-content>) and 2.0 mg L<jats:sup>−1</jats:sup> benzylaminopurine (<jats:styled-content style="fixed-case">BAP</jats:styled-content>). Mass propagation conditions were established from <jats:styled-content style="fixed-case">MSC</jats:styled-content>s cultured in <jats:styled-content style="fixed-case">MS</jats:styled-content> liquid medium containing 0.05 mg L<jats:sup>−1</jats:sup> 2,4‐<jats:styled-content style="fixed-case">D</jats:styled-content> and 0.5 mg L<jats:sup>−1</jats:sup> <jats:styled-content style="fixed-case">BAP</jats:styled-content>. The fresh weight of the <jats:styled-content style="fixed-case">MSC</jats:styled-content>s per flask increased by more than 16 times in 14 days of liquid culture. Two different sizes of <jats:styled-content style="fixed-case">MSC</jats:styled-content>s were produced in liquid culture. When smaller <jats:styled-content style="fixed-case">MSC</jats:styled-content>s (<2 mm in diameter) were transferred to half‐strength hormone‐free <jats:styled-content style="fixed-case">MS</jats:styled-content> solid medium, plant regeneration occurred at high frequency (93.3%). These tissues showed high regenerative potential with approximately 350 green shoots recovered within 50 days from 60 regenerating clumps. Furthermore, root elongation was vigorous in the regenerants growing in the same medium. Regenerated plants were acclimatized in hydrated <jats:styled-content style="fixed-case">J</jats:styled-content>iffy‐7 pellets for 30 days and then grown in soil as nursery plants. The plant height of regenerants was almost the same as original dwarf cogongrass and significantly lower than the wild type plants (<jats:italic>P </jats:italic><<jats:italic> </jats:italic>0.01). Analysis of amplified fragment length polymorphism (<jats:styled-content style="fixed-case">AFLP</jats:styled-content>) banding patterns generated using 10 primer combinations showed no major genetic variations among the regenerated plants and original dwarf cogongrass.</jats:p>